This invention relates to an industrial robot and more particularly, to a portable joint type robot for use in welding large scale structures and the like.
Development of industrial robots has made a remarkable progress in recent years and an extremely wide variety of robots have been announced. These robots can be classified structurally into a rectangular coordinate type robot, a cylindrical coordinate type robot, a polar coordinate type robot and a joint type robot. The robots of these types have their respective features and have been used in fields corresponding to the features. Among them, the joint type robot having high freedom has recently drawn an increasing attention because it can secure a greater operation range with respect to the installation area than the others.
In any way, most of the industrial robots of the kind described above are of the fixed installation type and weigh from one to several hundreds of kilograms. Hence, they can not easily be moved from one installation position to another. Although a robot having the main body weight of as small as about 10 kg has been developed at present, it is not suitable for welding or the like because a maximum portable weight is up to 1 kg. In other words, a tool to be held by a small robot is substantially the same as that of a large robot and hence, a conventional portable robot using small motors and reduction gears has so low capacity that it can not operate while holding a tool that is generally used by a skilled laborer, and high speed high acceleration operation can never be expected. If a large wrist driving motor is used in order to increase the portable weight of the robot, however, the main body construction becomes larger in scale and if this problem is to be avoided, the operation region of a small robot must be drastically reduced due to the limitation of these driving devices.
To reduce the size and weight, the design of such a small robot is difficult and the arrangement of each constituent member is also difficult. Accordingly, the robot performance is sometimes sacrificed to design the small robot.